A clinical device for measuring internal-external rotational laxity of the knee.

BACKGROUND: The dial test can be improved by providing reproducible, accurate measurements to improve diagnosis and treatment comparisons. PURPOSE: Validation of a rotational measurement device (RMD) for measuring knee internal-external rotational laxity. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: The RMD consisted of 3 components: a femoral clamp and a tibial splint using paired inclinometers to measure rotations, and a boot to apply tibial internal-external rotation torque. A separate boot inclinometer allowed for foot rotations to be measured independently. The measurements were simultaneously compared with electromagnetic "nest of birds" (NOB) sensors. Sequential paired knee measurements were taken at 4, 6, and 8 N·m of torque at 30° and 90° of flexion in 46 volunteers. RESULTS: The correlation coefficient was 0.92 (95% CI, 0.89 to 0.94) and 0.63 (95% CI, 0.54 to 0.70) between the NOB and RMD and between the NOB and boot inclinometer, respectively. Bland-Altman analysis revealed that the RMD was on average within 2° (95% CI, 1° to -4°) of NOB readings, whereas the boot overestimated by 34° (95% CI, -9° to -58°). Maximum side-to-side differences measured by the NOB, RMD, and boot were 1°, 3°, and 21°, respectively. The mean +2× standard deviation data gave a range of side-to-side differences of less than 5° for the RMD. The intraobserver intraclass correlation was 0.9 (95% CI, 0.78 to 0.97) at both 30° and 90° of flexion, and the 95% CI of the differences between readings taken on 2 occasions, the interobserver repeatability, was 1° or less. CONCLUSION: The novel clinical RMD for measuring rotational laxity of the knee was portable, easy, and comfortable to use in the clinical setting. The RMD showed significant correlation and accuracy compared with sensors of known high accuracy. Side-to-side differences of less than 5° were found in 95% of normal knees, compared with differences of 13° or more for clinical diagnosis of pathological rotational laxity. Measuring knee rotation at the foot showed poor correlation and accuracy.

Measurement of rotational laxity of the knee: in vitro comparison of accuracy between the tibia, overlying skin, and foot.

BACKGROUND: Posterolateral corner (PLC) injuries are difficult to diagnose and cause significant morbidity. The ideal method for the dial test and its accuracy remain unclear. PURPOSE: This study compares the accuracy of measuring tibial external rotation at the skeletal level to measuring the patella-tubercle angle (PTA) and the thigh-foot angle (TFA) in the supine position to assess the most accurate method to measure rotation during the dial test. STUDY DESIGN: Controlled laboratory study. METHODS: Measurements were compared simultaneously using rotational goniometers at a cutaneous splint over the tibia, at a foot splint, and directly from the tibial skeleton. Six lower limbs were used. The femur was held rigidly and the knee tested at 90° and 30° of flexion. External rotation torque up to 8 N·m was applied through the foot splint, and the rotations were measured by 2 testers. RESULTS: Measurements at the tibial splint and directly on the tibia showed significant correlation at both knee flexion angles. The mean tibial external rotation was 24° at 90° of flexion and 26° at 30° of flexion (P < .05). The soft tissue effect caused the tibial splint to overestimate rotations by a mean of 6° and 9° at 90° and 30° of flexion, respectively. Foot splint measurements did not correlate significantly with tibial rotation, overestimating rotations by a mean of 103%. Intratester and intertester intraclass correlations were significant for the skin-mounted tibial splint measurements at both flexion angles but not for foot splint measurements at either flexion angles. CONCLUSION: Rotation of the foot did not accurately represent the tibial external rotation at the knee, which could be measured more accurately by an instrument resting on the skin via a molded tibial splint. These results suggest that the PTA, and not the TFA, should be used in the dial test. This would support the use of the supine position during the dial test. CLINICAL RELEVANCE: The dial test is a commonly used method for diagnosing PLC injuries. This study helps to identify the ideal position and measuring points to use for this test; measurements based on the tibia were more accurate than those that used rotation of the foot.

Ankle ligament injuries.

Ankle ligament injuries in the presence or in the absence of fractures are common. They often present a diagnostic challenge, and their management is poorly understood and subject to debate. This article reviews and discusses the current literature on the management and diagnosis of these injuries.

The role of the medial collateral ligament and posteromedial capsule in controlling knee laxity.

BACKGROUND: The medial aspect of the knee has a complex capsular structure; the biomechanical roles of specific structures are not well understood. HYPOTHESIS: The 3 strong stabilizing structures, the superficial and deep medial collateral ligaments and the posteromedial capsule, make distinct contributions to controlling tibiofemoral laxity. STUDY DESIGN: Controlled laboratory study. METHODS: Changes in knee laxity under anterior-posterior drawer, valgus, and internal-external rotation loads were found by sequential cutting in 18 cadaveric knees. Three cutting sequences allowed the roles of the 3 structures to be seen in isolation and in combination. Some force contributions were also calculated. RESULTS: The posteromedial capsule controlled valgus, internal rotation, and posterior drawer in extension, resisting 42% of a 150-N drawer force when the tibia was in internal rotation. The superficial collateral ligament controlled valgus at all angles and was dominant from 30 degrees to 90 degrees of flexion, plus internal rotation in flexion. The deep collateral ligament controlled tibial anterior drawer of the flexed and externally rotated knee and was a secondary restraint to valgus. CONCLUSION: Distinct roles in controlling tibiofemoral laxity have been found for these structures that vary according to knee flexion and tibial rotation. CLINICAL RELEVANCE: The restraining functions demonstrated provide new information about knee stabilization, which may allow better evaluation of structural damage at the medial aspect of the knee.

RSA can measure ACL graft stretching and migration: development of a new method.

UNLABELLED: We describe the development of a method using radiostereometric analysis to measure fixation slippage and graft stretching after anterior cruciate ligament reconstruction. Initial development used a glass phantom object, then a series of laxity measurements of cadaveric knees. After this, we prospectively studied 14 patients after anterior cruciate ligament reconstruction using bone-patellar tendon-bone and hamstrings grafts. Tantalum markers were inserted into the femur, the tibia, and the graft. Radiostereometric analysis was used to measure sagittal laxity, graft stretching, and fixation slippage postoperatively and at intervals up to 1 year after surgery. The cadaveric knee laxity measured by RSA correlated with clinically-accepted KT2000 measurements. A steady increase in total anteroposterior laxity was found in both clinical groups during the year of followup. Migration of the bony fixations and stretching of the grafts tended to be higher in the hamstrings group. This method of anterior cruciate ligament graft analysis provides a new way to ascertain laxity changes in the reconstruction after surgery. LEVEL OF EVIDENCE: Diagnostic Level II. See Guidelines for Authors for a complete description of levels of evidence.

Arthroscopic appearances of the meniscofemoral ligaments: introducing the "meniscal tug test".

To evaluate the feasibility of identifying the anterior and posterior meniscofemoral ligaments (aMFL and pMFL, respectively) at arthroscopy, both visually and using the "meniscal tug test", which exploits the anatomical attachments of the posterior cruciate ligament (PCL) and MFLs. This is an observational type of study. Arthroscopy using anteromedial and anterolateral portals was performed in 68 knees in 68 patients (36 right, 32 left). The MFLs were identified using several anatomical cues, including their femoral and meniscal attachments, their obliquity relative to the PCL, and the meniscal tug test. Identification was classed as easy or hard by the operating surgeon. From 68 knees, the aMFL was seen and confirmed to be an MFL using the tug test in 60 (88%). Identification of the aMFL was classed as easy in 64 (94%), whilst the pMFL was easy to identify in only 6 (9%) of knees, of which 3 had a ruptured PCL. Thus, with the exception of PCL-deficient knees, it was felt that the meniscal "tug test" as applied in this study was not suitable for the pMFL. The study shows that identification of the aMFL is possible in most knees at arthroscopy, using the "tug test" and other anatomical cues. However, identification of the pMFL may require a posterior portal. A subgroup of PCL injuries in which the MFLs were intact was also observed. The "meniscal tug test" can be used in arthroscopic examinations of the PCL to distinguish between fibres of the true PCL from the MFLs, thus avoiding the misdiagnosis of partial versus complete PCL rupture. This will also aid studies examining the role of the MFLs in stabilising the PCL-deficient knee.

Synovial shelves of the knee: association with chondral lesions.

The objectives of the present study were to evaluate whether synovial shelves of the knee are associated with increased incidence of chondral lesions and to determine which types of plica are associated with significant articular damage. Data were collected prospectively from 1,000 consecutive knee arthroscopies. Of these patients, 321 (32.1%) were found to have synovial shelves of the knee. Patients details (age, sex, duration of symptoms, injuries, and possible mechanism of injury), operative details (types and number of portals, equipment used), intra-articular findings (articular, meniscal and synovial lesions, and stability characteristics) and procedures performed were recorded on a special database. Synovial shelves of the knee were recorded using a modification of the Sakakibara classification. Articular lesions were noted on anatomic articular maps of the different functional zones using a functional zoning system that presaged the current ICRS system. An increased incidence of articular lesions was found in patients with synovial shelves, in comparison with patients without shelves (94.7 vs. 81% respectively; P < 0.001). Patients with larger and more fibrotic shelves were found to have increased incidence of cartilage lesions, in comparison with patients with type smaller and less fibrotic shelves (96.5 vs. 86.4%, respectively; P = 0.002), as well as cartilage lesions with bigger size (84 vs. 71.4%, respectively; P = 0.02). Patella (P < 0.001), and specific areas (P < 0.001) of the medial femoral condyle, were areas with increased incidence of cartilage lesions, in patients with synovial shelves. In conclusion, synovial shelves of the knee are associated with an increased incidence of cartilage lesions. Larger shelves, particularly with chronic inflammation are associated with more frequently occurring and larger articular lesions. Areas with increased incidence of chondral lesions, in patients with plicae, include particularly the lower patella and the non-weight-bearing medial femoral condyle.

Magnetic resonance imaging of the knee with ultrashort TE pulse sequences.

BACKGROUND: We wished to assess the feasibility of imaging the knee with ultrashort TE (UTE) pulse sequences. SUBJECTS AND METHODS: Five volunteers and 16 patients were studied with UTE (TE=0.08 ms) sequences including later echoes. Conventional fat-suppressed images and difference images were also produced by subtracting a later echo from the first. Gadodiamide enhancement was used. RESULTS: High signal was obtained in tendons, ligaments, menisci and periosteum. Normal contrast enhancement was seen in these structures. Deep and superficial layers were seen in the articular cartilage. Cartilage defects were identified. The red zone could be differentiated from the white zone of the meniscus. Meniscal tears and degeneration were observed with low signal on subtraction images. Enhancement was seen within the anterior and posterior cruciate ligaments and associated scar tissue. CONCLUSION: Ultrashort TE imaging provides new options to visualize anatomy, manipulate conspicuity, observe contrast enhancement and demonstrate disease of the knee.

The meniscofemoral ligaments: secondary restraints to the posterior drawer. Analysis of anteroposterior and rotary laxity in the intact and posterior-cruciate-deficient knee.

We have tested the hypothesis that the meniscofemoral ligaments make a significant contribution to resisting anteroposterior and rotatory laxity of the posterior-cruciate-ligament-deficient knee. Eight cadaver human knees were tested for anteroposterior and rotatory laxity in a materials-testing machine. The posterior cruciate ligament (PCL) was then divided, followed by division of the meniscofemoral ligaments (MFLs). Laxity results were obtained for intact, PCL-deficient, and PCL-MFL-deficient knees. Division of the MFLs in the PCL-deficient knee increased posterior laxity between 15 degrees and 90 degrees of flexion. Force-displacement measurements showed that the MFLs contributed 28% to the total force resisting posterior drawer at 90 degrees of flexion in the intact knee, and 70.1% in the PCL-deficient knee. There was no effect on rotatory laxity. This is the first study which shows a function for the MFLs as secondary restraints to posterior tibial translation. The integrity of these structures should be assessed during both imaging and arthroscopic studies of PCL-injured knees since this may affect the diagnosis and management of such injuries.

Meniscofemoral ligaments--structural and material properties.

The meniscofemoral ligaments (MFLs) of 28 human cadaveric knees were studied to determine their incidence, structural and material properties. Using the Race-Amis casting method for measurement, the mean cross-sectional area for the anterior MFL (aMFL) was 14.7 mm(2) (+/-14.8mm(2)) whilst that of the posterior MFL (pMFL) was 20.9 mm(2) (+/-11.6mm(2)). The ligaments were isolated and tensile tested in a materials testing machine. The mean loads to failure were 300.5 N (+/-155.0 N) for the aMFL and 302.5 N (+/-157.9 N) for the pMFL, with elastic moduli of 281 (+/-239 MPa) and 227 MPa (+/-128 MPa), respectively. These significant anatomical and material properties suggest a function for the MFL in the biomechanics of the knee, and should be borne in mind when considering hypotheses on MFL function. Such hypotheses include roles for the ligaments in knee stability and guiding meniscal motion.